Lubricating oil compositions



LUBRICATING OIL COR POSITIONS OliverLHarie, Berkeley, and John R.Thomas, Albany, Cahf., .assignors to California Research Corporation,San Francisco, Calif., a corporation of Delaware No Drawing. ApplicationJune 29, 1954, Seriai No. 440,250

2 Claims. (Cl. 252--49.6)

This invention relates to novel lubricant compositions. Moreparticularly, the invention is concerned with novel lubricating oilcompositions having improved oxidation and corrosion inhibitingproperties.

Lubricating oils generally have a tendency to deteriorate due tooxidation and form decomposition products which are corrosive to metals.Since lubricating oils in use today almost invariably come into contactwith metal surfaces, the problem of overcoming oxidation and corrosionis considered to be one of major importance. Operating conditionsencountered in modern internal combustion engines in which these oilsare commonly employed involve increased temperatures, higher speeds andreduced clearances which tend to promote decomposition and the formationof corrosive products. Furthermore, these engines generally employ alloymetal bearings which, besides their possible catalytic effect on thedecomposition 'of the hydrocarbon type mineral lubricating oils, areeasily corroded and this, in turn, has seriously accentuated theoxidation and corrosion problems in mineral lubricating oils.

Inhibitors have been added to lubricating oils to improve theirresistance to decomposition and avoid corrosivity. Mineral lubricatingoils for internal combustion engines, due to the severity of theirservice, have also been compounded with additional agents such as wearinhibitors, sludge inhibitors and detergents to loosen and suspendproducts of decomposition and counteract their effect. Unfortunately,many of these agents may adversely affect the efficiency of theoxidation and corrosion inhibitors and it is a problem to findinhibitors which will function in combination with them. Furthermore,some of the most effective oxidation and corrosion inhibitors containactive sulfur and are, therefore, extremely corrosive to silver andsimilar metals which are subject to attack by active sulfur. These typesof metals, although once not so widely used in contact with lubricatingoils and therefore considered to constitute only a minor problem, arebeing increasingly employed today. Particularly in certain importantclasses of internal conbustion engines as, for example, marine andrai.road diesel engines, silver metal-containing bearings are more andmore common and the problem of providing proper lubrication for them isone of major importance.

It is, therefore, a general object of this invention to providelubricating oil compositions having improved antioxidant andanticorrosion properties.

A more particular object of the invention is to provide lubricating oilcompositions which are noncorrosive to silver and similar metals.

Another more particular object is the provision of mineral lubricatingoil compositions in which the tendency to corrode alloy bearings ofinternal combustion engines has been inhibited.

A further and somewhat related object is to provide compounded minerallubricating oil compositions having improved anticorrosion propertieswithout adversely afiect- Patented June 11,1957

ing the stabilizing, deterging and lubricating qualities of thehydrocarbon oil composition.

Another and still more particular object of the invention is theprovision of mineral lubricating oil compositions which are noncorrosiveto silver metal-containing bearings of the type employed in railroaddiesel engines.

Additional objects of the invention will become apparent from thedescription and claims which follow.

In the accomplishment of the above objects, it has been found thatcompositions comprising an oil of lubricating viscosity and a complex ofa metal compound selected from the group consisting of acids, oxides andsalts of boron with a metal chelating agent having two functionalgroups, not more than one of which is a hydroxyl radical, in vicinal orbeta position to one another on the carbon skeleton of a hydrocarbonlinkage have greatly enhanced anticorrosion properties. It has also beenfound that, in particular, compositions comprising a compounded minerallubricating oil for internal combustion engines which is normallycorrosive to alloy bearings and such chelates are substantiallynoncorrosive.

The metal chelating agent referred to above is the accepted terminologyfor a definite and well-known class of chemical compounds. Suchcompounds have been heretofore described in many published textsincluding the recent book entitled Chemistry of the Metal ChelateCompounds by Martell and Calvin which was published by Prentice-Hall,Inc. of New York in 1952. For present purposes the more suitablecompounds of this class are members of the group consisting of dithiols,diamines, mercapto alcohols, amino alcohols, amino thiols, dicarboxylicacids, hydroxycarboxylic acids, mercaptocarboxylic acids,aminocarboxylic acids, beta-diketones, beta-keto carboxylic acid esters,dimercapto benzenes, mercaptohydroxy benzenes, diamino benzenes,aminohydroxy benzenes, aminomercapto benzenes, hydroxycarboxy benzenes,aminocarboxy benzenes, and mercaptocarboxy benzenes having the twofunctional groups in vicinal or beta position to one another on thecarbon skeleton.

The normal tendency of oils to become oxidized and corrosive isdefinitely inhibited in the improved compositions of the invention.Metal surfaces in general are not corroded by contact with thesecompositions and internal combustion engine alloy bearings, inparticular, are remarkably benefited. Bearings of silver and similarmetals which, as stated above are increasingly important due to theirpresent expanded use in marine and railroad diesel engines, are notcorroded by these compositions whereas conventional oxidation inhibitedoils have severely pitted and corroded such bearings. The advantages ofthese improvements are obtained in the compositions of this inventionwithout loss of stability or detergency in the composition.

The complexes of the lubricating oil compositions according to thisinvention are prepared by the reaction of a mixture of the acid, oxideor salt of boron and chelating agent. The mixtures are ordinarily heatedto accelerate the reaction. Although the nature of the reaction is notdefinitely known, it is believed that two of the functional groups of asingle ketocarboxylic acid ester, dithiol, dicarboxylic acid, etc. reactwith the acid to form what is commonly termed a metal chelate compound.These compounds are characterized by a claw type of structure in whichone or more rings of similar or unlike structure due to the use of mixedchelating agents are formed including the boron.

The preferred chelates of the above type are oil-soluble and thechelating agents are usually selected so as to impart oil solubility tothe complex or chelate. Chelating agents containing from 2 to 18 carbonatoms are usually suitable since the less oil-soluble chelates may beused in combination with dispersants such as alkaline earth metalpetroleum sulfonates or oil-solubilizing agents such as glycols andother polyhydric alcohols as well as ethers thereof. Those containingfrom 6 to carbon atoms in the carbon skeleton are preferred since theyimpart an optimum degree of oil solubility to the chelate or complex.

Examples of suitable chelating agents within the above- 7 describedclass include vicinaland beta-dithiols such as ethylene mercaptan and1,3-propanedithiol; vicinaland beta-mercapto alcohols such asbeta-mercaptoethanol, 3- mercapto-l-propanol; vicinaland beta-diaminessuch as ethylenediamine and propylenediamine; vicinaland betaaminoalcohols such as ethanolamine and S-amino-lpropanol; vicinalandbeta-aminothiols such as thioethanolamine and 3-amine-l-mercaptopropane;vicinaland beta-dicarboxylic acids such as oxalic acid and malonic acid;vicinaland beta-hydroxy carboxylic acids such as glycolic acid andbeta-hydroxybutyric acid; vicinaland beta-mercapto carboxylic' acidssuch as thioglycolic acid and beta-mercaptobutyric acid; vicinalandbeta-amino carboxylic acids such as glycine and beta-aminobutyric acid;beta-diketones such as acetylacetone and benzoylacetone;beta-ketocarboxylic acid esters such as ethyl acetoacetate; etc. Theforegoing compounds are characterized by normal or branched carbonskeletons. They may have substituted in various positions along thecarbon skeleton, aromatic and substituted aromatic rings; hydroxy,alkoxy, and aryloxy radicals; sulfhydryl, alkylthioether, arylthioether,alkylthioester, and arylthioester groups; acyl, aroyl thioacyl andthioaroyl radicals; amino, alkylamino, arylamino, acylamido andaroylamido radicals; and nitro, halogen and sulfato groups. However,preferred chelating agents of the aforementioned type for presentpurposes are those having an aliphatic hydrocarbon group between the twofunctional groups.

Also suitable as chelating agents are various carbocyclic or aromaticchelating agents including dimercaptoaromatic compounds such asthiocatechol; vicinal-mercaptohydroxy aromatic compounds such asmonothiocatechol or mercaptohydroxy benzene; vicinal-diarninoaromaticcompounds such as o-phenylenediamine; vicinal-aminohydroxyaromaticcompounds such as o-aminophenol; vicinalaminomercaptoaromatic compoundssuch as o-aminothiophenol; vicinal-hydroxycarboxyaromatic compounds suchas salicylic acid; vicinal-aminocarboxyaromatic compounds such aso-aminobenzoic acid; vicinal-mercaptocar boxyaromatic compounds such aso.-mercaptobenzoic acid; etc. The aforementioned carbocyclicor aromaticchelating agents may have various ring substituents including aromaticand substituted aromatic rings; hydroxy, alkoxy, and aryloxy radicals;sulfhydryl, alkylthioether, arylthioether, alkylthioester, andarylthioester groups; acyl, aroyl, thioacyl and'thioaroyl radicals;amino, alkylamino, arylamino, acylamido, and aroylarnido radicals; andnitro, halogen and sulfate groups. For present purposes those aromaticchelating agents having the two functional groups on a benzene ring oran alkyl benzene containing from 2 to 18 carbon atoms in the alkyl groupare preferred .since the chelates of the above-described metals preparedwith them possess the most satisfactory oil-solubility characteristics.

For present purposes the chelating agents most preferred out of theabove-described classes are the beta-ketocarboxylic acid esters of from4 to 18 and. preferably 4 to 10 aliphatic carbon atoms. Illustrativechelating agents of this particular group are ethyl acetoacetate, ethylacetobutyrate, acetoacetic acid, pyruvic acid, etc. These chelatingagents give complexes of the previously described types which aresuperior corrosion and/ or oxidation inhibitors in the lubricating oilcompositions of the invention.

Although it is convenient for the sake of illustration in the abovedescription of the invention torefer to the reaction of an acid of theboron with the various chelating agents or mixtures thereof to form thecomplexes for the lubricating oil compositions, other compounds of boronsuch as the oxides and salts mentioned above may also be employed toprovide similar chelates. Suitable boron compounds include boricanhydride, boron trichloride and other similar acting reagents.

The complex of boron described above is present in the compositions ofthe invention in an amount at least suflicient to inhibit corrosion oroxidation. Small amounts, usually from about 0.01 to about 5.0 percentby Weight based on the oil, are efiective. Proportions ranging fromabout 0.05 to about 1.0 percent are preferred in most lubricating oilcompositions. Concentrates containing larger proportions, up to 50percent, either in solution or suspension, are particularly suitable incompounding operations.

Any of the well-known types of oils of lubricating viscosity aresuitable base oils for the compositions of the invention. They includehydrocarbon or mineral lubricating oils of naphthenic, paraflinic, andmixedfnaphthenic and paraffinic types. They may be refined by any of theconventional methods such as solvent refining and acid refining.Synthetic hydrocarbon oils of the alkylene polymer type or those derivedfrom coal and shale may also be employed. Alkylene oxide polymers andtheir derivatives such as the propylene oxide polymers and their ethylesters and acetyl derivatives. in which the terminal hydroxyl groupshave been modified are also suitable. Synthetic oils of the dicarboxylicacid ester type including dibutyl adipate, di-Z-ethylhexyl sebacate,di-n-hexyl fumaric polymer, dilauryl azelate, and the like may be used.Alkyl benzene types of synthetic oils such as tetradecyl benzene, etc.are also included. Liquid esters of acids of phosphorus includingtricresyl phosphate, diethyl esters of decane phosphonic acid, and thelike may also be employed. Also suitable are the polysiloxane oils ofthe type of polyalkyl, polyaryl, polyalkoxy and polyaryloxy siloxanessuch as polymethyl siloxane, polymethylphenyl siloxane andpolymethoxyphenoxy siloxane and silicate ester oil-s such as tetraalkyland tetraaryl silicates of the tetra-Z-ethylhexyl silicate andtetra-p-tert.-butylphenyl silicate types.

In a preferred embodiment of the invention, as mentioned above, thecomplexes are employed in combina- .the case of the other, straight oilsof lubricating viscosity,

a major proportion of the lubricating oil normally corrosive to metalsand/or subject to oxidation and a small amount, suflicient to inhibitsaid corrosion and/ or oxidation, of the complex provides a remarkablyimproved composition. These compounded oils customarily containdetergents such as the oil-soluble petroleum sulfomates and stabilizerssuch as the metal alkyl phenates. Other agents such as oiliness agents,viscosity index improvers, pour point depressants, blooming agents,peptiz- ,ing agents, etc. may also be present.

In further illustration of the invention, the following examples aresubmitted showing the preparation of representative complexes andevaluation of their eifectiveness as corrosion inhibitors andantioxidants in oil composition. Unless otherwise specified theproportions given in these examples are on a Weight basis.

EXAMPLE A mixture of two moles of ethyl acetoacetate and one mole ofboric acid in 300 milliliters of benzene is charged to a glass reactionflask equipped with stirring mechanism, reflux condenser and waterseparation trap. The mixture is refluxed with continuous waterseparation until it becomes homogenous. The product containing the boronethyl acetoacetate formed in the reaction is then concentrated to acolorless viscous liquid by evaporation of the benzene and used as aconcentrate in blending test oils.

The effectiveness of the lubricating oil compositions of the inventionis demonstrated by the Copper-Lead Strip Percent by weight Iron 0.008Lead 0.004 Copper 0.002 Manganese 0.0005 Chromium 0.004

In the tests the reference oil is a compounded oil which consists of asolvent refined SAE 40 mineral lubricating oil base having a viscosityindex of 60 and containing millimoles per kilogram of neutral calciumpetroleum sulfonate and millimoles per kilogram of calcium alkylphenate, sulfurized. The results of the test are shown in the followingtable. The concentrations of complex employed are given in rnillimolesof boron per kilogram of oil or percent by weight of the composition.

Table I COPPER-LEAD STRIP CORROSION TEST As shown by the above testdata, the reference mineral lubricating oil composition alone givescopper-lead strip Weight losses due to corrosion of over 250 milligramsin the 20-hour period. By way of distinction, compositions in accordancewith this invention containing the same mineral lubricating oil base anda complex of the previously described type give as little as 2.0milligrams for the same period. This shows that the compositions of thepresent invention are effectively inhibited against oxidation and/orcorrosion characteristics due to the oxidative deterioration of the oil.

Compositions which comprise a major portion of a compounded oil oflubricating viscosity having a base reserve and a minor portion at leastsufiicient to enhance the resistance of said oil against base depletiondue to oxidation of a complex of the above type constitute anotherembodiment of this invention. Such base reserve oils contain additivessuch as basic alkaline earth metal sulfonates, alkaline earth metalalkyl phenates, alkaline earth metal salts of hydroxy phenyl sulfidesand disulfides, etc. in amounts to give the composition a pH on thealkaline side, i. e., 10 or so. Ordinarily, 0.01 to 10.0% is sufiicient.The proportions of boric acid complex apply here as mentioned above.

In the Navy propulsion load test described in MIL-P- 17269 (Ships) July17, 1952, the compositions of the invention are evaluated as dieselengine lubricating oils under severe operating conditions. The tests arerun in a General Motors 4-cylinder diesel engine using one percentsulfur fuel. Copper-lead bearings are employed. The tests are run at aconstant speed of 1800 R. P. M. under 2. load of brake horsepower percylinder. The

crankcase temperature is 250 F. The present test is run continuously tosimulate railroad diesel engine performance unlike the standard Navytest procedure which permits regular 4-hour shutdown periods. Sea waterwas also excluded for the same reason. The reference oil, as before, isa solvent refined SAE 40 mineral lubricating oil base having a viscosityindex of and containing 10 mM/kg. of neutral calcium petroleum sulfonateand 20 mM/kg. of calcium alkyl phenate, sulfurized. Test results are asfollows:

Table II Weight Loss mgsJW hole Bearing (Hours) Oil Reference oil 70 8302, 000 2.0% boron ethyl acetoacetate in reference oil. 31 50 In the Navypropulsion load test results shown above, the bearing weight loss due tocorrosion by the reference oil, a conventional heavy duty compoundedoil, was extremely high. Such an oil would be impossible to use for anyprolonged period of time without shutdown. By way of distinction, thelubricating oil composition of the invention containing borate complexesgives remarkably low corrosion losses after as much as 150 hours ofcontinuous operation. Greatly extended periods of uninterruptedoperations of diesel engines are thus possible with these improved oils.

The nature of the. improved lubricating oil compositions of theinvention and their effectiveness should be readily apparent from themany'illustrations, given above. Oxidation and corrosivity in thecompositions are definitely inhibited to a very substantial degree.Particularly corrodible metals such as engine alloy bearings of copper,lead, and the like, as well as bearings of silver, are not adverselyaffected. This is indeed remarkable since the problem of devisinglubricant compositions uniformly noncorrosive to both types of bearingmetals has long confronted workers in the art. The advantages of theseimprovements are obtained without loss of other desirable properties ofthe lubricant compositions.

Although the compositions of the invention have been primarily describedas crankcase lubricants for internal combustion engines, they are alsouseful as turbine oils, hydraulic fluids, instrument oils, constituentoils in grease manufacture, ice-machine oils, and the like.

We claim:

1. A lubricant composition comprising an oil of lubricating viscosityand boron ethyl acetoacetate in an amount sufficient to inhibitcorrosion.

2. A lubricant composition comprising a mineral lubricating oil forinternal combustion engines which is normally corrosive to alloybearings and from about 0.01 to about 5.0 percent by weight based on theoil of boron ethyl acetoacetate.

References Cited in the file of this patent UNITED STATES PATENTS2,144,654 Guthmann et al J an. 24, 1939 2,161,184 McKone et al June 6,1939 2,305,627 Lincoln et al Dec. 22, 1942 2,465,296 Swiss Mar. 22, 1949

